Switch mode power converters can be used in a wide variety of applications. The mode of operation of a switch mode power converter typically depends on the type of application. Even within the same type of application, the operation note of a switch mode power converter may depend on the specific application.
Taking as an example switch mode power converters used as LED lighting drivers, requirements on such LED lighting drivers, especially those for retrofit LED lamps, also known as solid state lighting (SSL), differ according to region and according to lamp supplier. For instance, the character of the lamp impedance to the mains, often measured through power factor (PF) and total harmonic distortion (THD) is tied to requirements which differ by region, by market (e.g. consumer markets and professional markets) and by lamp power range.
Further, preferences of SSL lamp suppliers result in different requirements on the driver. A minimum physical size will result in a driver operating at a high switching frequency to minimize inductive components, while a focus on maximum power conversion efficiency will result in a lower switching frequency, offering lower losses at the cost of a somewhat larger physical volume.
Moreover, dimmable SSL drivers for retrofit use are generally required to detect presence of a wall dimmer, to ensure operation as intended and to interpret the phase angle of the output signal of the dimmer as a dimming level to be applied to the lamp light output. Lamp suppliers as well as standardization bodies recommend several so-called “dim curves”, which define the relation between detected dimming angle and light output. Dim curves can either be optimized for best user experience, best compatibility to a certain dimmer range, or for lowest power dissipation.
The operation modes described above can all be integrated in an SSL driver at very limited additional cost, especially in case digital circuitry is used. However, in common with drivers for switch mode converters intended for other types of applications, the continuous drive to reduce system cost and size has resulted in SSL drivers with just 6 or 8 connection pins which cover the minimum connections required. As a result, no pins are available to provide input to the driver, regarding the desired operational mode. Typically, then, in consequence multiple products are designed and manufactured, specific to individual operational modes, based on a single design base. This may result in a high, and thus expensive, inventory, and relative inflexibility of supply of the driver ICs.